Stem cells, gene therapy, transplants, and cloning have changed the definition of "humanity" in the modern world, but the darker side contains monsters that only few are brave enough to face, because the future lies in their hands.

The show centers on Dr. Helen Magnus, a 157-year-old teratologist (born August 27, 1850), and her team of experts who run the Sanctuary, an organization that seeks out extraordinarily-powerful creatures and people, known as Abnormals, and tries to help and learn from them, while also having to contain the more dangerous ones.